1. Field of the Invention
This invention relates generally to a patterned-media magnetic recording disk drive that has disks with discrete magnetizable data islands, and more particularly to a read/write head positioning servo control system in such a disk drive.
2. Description of the Related Art
Magnetic recording hard disk drives with patterned magnetic recording disks have been proposed to increase the data density. In patterned media, the magnetic recording layer on the disk is patterned into small isolated data islands or “dots” that represent individual data “bits”. Like conventional non-patterned disks, patterned-media disks are also required to have nondata servo sectors that are used for read/write head positioning. The nondata servo sectors contain servo fields that generate readback signals that, when decoded, provide radial and circumferential position information about the read/write head. This information in turn is used by the servo system in moving the read/write head to the desired data track and maintaining it on track. In patterned-media disks the servo sectors typically contain patterned servo blocks separated by nonmagnetic spaces. However, the complexity of typical servo patterns and the requirement for their precise alignment with the patterned data tracks make the use of conventional servo patterns difficult in patterned-media disk drives.
In disk drives with conventional non-patterned disks, the servo patterns are written either by a dedicated servowriter or by the disk drive's write head in a technique referred to as self-servowriting. In patterned-media disk drives the discrete servo blocks are required to be magnetized in specific magnetization directions so as to generate the desired readback signal. However, the required precision to write the desired patterns at specific disk locations is very difficult to accomplish using a conventional servowriter or self-servowriting method.
What is needed is a patterned-media magnetic recording disk drive with an improved servo control system and an improved method for self-servowriting the nondata servo sectors.